A common task encountered in photographic retouching involves the correction of localized flaws in images. These flaws may consist of scratches, dust, wrinkles, blemishes, or other perceived “imperfections.” For example, a still-life photograph of a strawberry might exhibit all black seeds, except for a single white seed. In order to “fix” the white seed, by replacing it with a black one, a user can utilize a tool to copy an existing black seed over the white one. The graphical process of copying one area onto another is commonly referred to by those of ordinary skill in the art as “cloning”.
Existing cloning tools allow a ser to correct flaws by defining a “source” location and brushing across the “destination” area. In the previous example, a user would define an area near a typical black seed and brush across the “destination” area containing the white seed. The result is a duplicate copy, or “clone,” of the black seed, covering the white seed and thus providing the desired photographic result. An example of a prior art program that utilizes such a cloning tool is Adobe Photoshop™. The tool commonly referred to as the Clone Stamp provides users with the ability to duplicate one area of an image onto another area of that same image.
This image cloning technique is very powerful, and constitutes one of the workhorses of digital image retouching. However, existing clone tools have very significant limitations. For instance, current image cloning tools may sometimes copy too much information. For example, consider a photograph of a person's wrinkled face. An artist might be asked to retouch the photograph to “remove” the wrinkles, replacing them with smooth skin. Existing image cloning tools facilitate this process by “cloning” smooth areas of skin to cover the wrinkled areas, thus eliminating the wrinkles from the photograph. However, if the overall shades of the source and destination areas do not match precisely, the cloning process can create discolored blotches on the image. This limitation further reduces the effectiveness of the cloning when there are few suitable source regions that match the shade of the areas where retouching is desirable.
Another approach for retouching minor scratches, dust, and film grain within a single image uses small fixed radius smoothing filter to produce a smoothed image, from which a texture information layer is generated, of equal size to the original image. These processing steps are applied in advance to the entire image, creating a substantial delay. Straightforward cloning is then performed on the texture information layer, which is eventually re-integrated with the filtered image to produce a result image. While adequate for manipulating small-scale textures in some limited circumstances, this tool is entirely ineffective for processing larger-scale textures of the variety encountered in a modern digital image-retouching environment. Therefore, a need for a significantly more powerful and efficient texture processing apparatus is evident.